Soft Starter for High-Current Electric Devices

ABSTRACT

An inrush current limiting circuit in aspects of the present disclosure may have one or more of the following features: a printed circuit board, an electrical input disposed on the circuit board, one or more electrical outputs disposed on the circuit board, a current limiting circuit connected between the electrical input and the one or more electrical outputs, at least one microcontroller connected within the current limiting circuit, at least one current sensor connected within the current limiting circuit, one or more current limiting components within the current limiting circuit for increasing voltage and current over time from the electrical input to the one or more electrical outputs by operation of the current sensor and the microcontroller.

PRIORITY STATEMENT

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 16/802,414, filed on Feb. 26, 2020 which claimspriority to U.S. Provisional Patent Application No. 62/810,735, filed onFeb. 26, 2019, both titled SOFT STARTER FOR HIGH-CURRENT ELECTRICDEVICES all of which are hereby incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The present disclosure relates to initial start-up of electric devices.Particularly, the present disclosure relates to an apparatus forcontrolling the inrush of current to one or more electric devices. Moreparticularly, but not exclusively, the present disclosure relates to anapparatus and method for controlling the inrush of current to electricdevices, such as high-current devices, through current restriction.

BACKGROUND

AC motor driven devices, such as power tools, garage door openers,conveyors, etc. undergo a loud and hard startup from the sudden inrushof electrical current. This can cause an unsafe and unpleasant userexperience. It can also cause dimming lights, tripped circuit breakers,as well as increased wear and tear to the motor driven devices, electriccurrent carrying and exposed components, and their attachments.

From the above, it is therefore seen that there exists a need in the artto overcome the deficiencies and limitations for powering ACmotor-driven devices.

SUMMARY

Therefore, it is a primary object, feature, or advantage of the presentdisclosure to improve over the state of the art.

According to at least on object of the present disclosure, an inrushcurrent limiting circuit is disclosed. The inrush current limitingcircuit can include, for example, a printed circuit board, an electricalinput disposed on the circuit board, one or more electrical outputsdisposed on the circuit board, a current limiting circuit connectedbetween the electrical input and the one or more electrical outputs, atleast one microcontroller connected within the current limiting circuit,at least one current sensor connected within the current limitingcircuit, and one or more current limiting components within the currentlimiting circuit for increasing voltage and current over time from theelectrical input to the one or more electrical outputs by operation ofthe current sensor and the microcontroller.

According to another object of the present disclosure, a method forlimiting inrush current is disclosed. The method can include, by way ofexample, one or more steps, such as, providing a current limitingcircuit having at least one microcontroller, at least one currentsensor, and one or more current limiting components having a presetcurrent level, configuring the one or more current limiting componentsto a reduced voltage and current potential by operation of the at leastone microcontroller, detecting current draw with the at least onecurrent sensor, and increasing current over time with the one or morecurrent limiting components by operation of the microcontroller if thecurrent exceeds the preset current level.

According to at least one other object of the present disclosure, amethod for limiting inrush current may have one or more of the followingsteps: (a) providing a housing enclosure having an electrical input andan electrical output, where at least one thermistor is in series withthe electrical input and electrical output and the at least onethermistor has a temperature switch coupled to the at least onethermistor and an axial cooling fan, (b) detecting an inrush of currentcause by a high-current device being powered on, (c) dissipating theinrush current with the at least one thermistor, (d) detecting atemperature of the at least one thermistor, (e) powering on the axialfan based upon the detected temperature of the at least one thermistor,(f) determining if the temperature of the at least one thermistor isabove a preset limit for the at least one thermistor, (g) powering offthe axial fan if the sensed temperature of the at least one thermistoris below a preset limit for the at least one thermistor, (h) bypassingthe at least one thermistor when the inrush current has subsided, and(i) determining elapsed time from the initiation of the inrush current.

An inrush current limiting circuit in aspects of the present disclosuremay have one or more of the following features: (a) an electrical inlet,(b) an electrical outlet, (c) a microcontroller operably coupled to thezero-crossing detector, (d) a triac/scr circuit operably coupled to themicrocontroller and the electrical outlet, (e) a current sensor operablycoupled to the electrical inlet, (f) a housing enclosure housing themicrocontroller and the triac/scr circuit, and (g) a zero-crossingdetector operably coupled to the current sensor.

An inrush current limiting circuit in aspects of the present disclosuremay have one or more of the following features: (a) a housing enclosure,(b) an electrical input located on the housing enclosure, (c) anelectrical output located on the housing enclosure, (d) at least onethermistor is in series with the electrical input and electrical output,(e) a temperature sensor coupled to the at least one thermistor and anaxial cooling fan, (f) at least one thermistor, where the temperaturesensor detects a temperature of the at least one thermistor, (g) theaxial fan electrically is powered on to cool the at least one thermistorwhen the temperature sensor detects the at least one thermistor is abovea pre-determined temperature, (h) a bypass circuit electrically coupledto an electrical input and the at least one thermistor, (i) amicrocontroller electrically coupled to the bypass circuit, (j) acurrent sensor electrically coupled with the microcontroller and the atleast one thermistor, (k) a PCB board supporting the at least onethermistor and the temperature sensor, and (l) an enclosed housinghaving at least one exhaust port.

One or more of these and/or other objects, features, or advantages ofthe present disclosure will become apparent from the specification andclaims that follow. No single aspect need provide every object, feature,or advantage. Different aspects may have different objects, features, oradvantages. Therefore, the present disclosure is not to be limited to orby any objects, features, or advantages stated herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrated aspects of the disclosure are described in detail below withreference to the attached drawing figures, which are incorporated byreference herein.

FIG. 1 is a pictorial representation of an inrush current limitingcircuit in accordance with an aspect of the present disclosure;

FIG. 2 is a pictorial representation of a housing enclosure inaccordance with an exemplary aspect of the present disclosure;

FIG. 3 is a pictorial representation of an inrush current limitingcircuit in accordance with an exemplary aspect of the presentdisclosure;

FIG. 4 is a pictorial representation of an inrush current limitingcircuit in accordance with an exemplary aspect of the presentdisclosure;

FIG. 5 is a pictorial representation of a housing enclosure inaccordance with an exemplary aspect of the present disclosure;

FIG. 6 is a flowchart diagram of an inrush current limiting circuitoperation in accordance with an exemplary aspect of the presentdisclosure;

FIG. 7A-C are pictorial representations of an inrush current limitingcircuit in accordance with another exemplary aspect of the presentdisclosure;

FIG. 8 is a flowchart diagram of an inrush current limiting operation inaccordance with another exemplary aspect of the present disclosure; and

FIG. 9A-C are pictorial representations of inrush current limitingenclosures in accordance with an exemplary aspect of the presentdisclosure.

Some of the figures include graphical and ornamental elements. It is tobe understood the illustrative aspects contemplate all permutations andcombinations of the various graphical elements set forth in the figuresthereof.

DETAILED DESCRIPTION

The following discussion is presented to enable a person skilled in theart to make and use the present teachings. Various modifications to theillustrated aspects will be clear to those skilled in the art, and thegeneric principles herein may be applied to other aspects andapplications without departing from the present teachings. Thus, thepresent teachings are not intended to be limited to aspects shown butare to be accorded the widest scope consistent with the principles andfeatures disclosed herein. The following detailed description is to beread with reference to the figures, in which like elements in differentfigures have like reference numerals. The figures, which are notnecessarily to scale, depict selected aspects and are not intended tolimit the scope of the present teachings. Skilled artisans willrecognize the examples provided herein have many useful alternatives andfall within the scope of the present teachings. While aspects of thepresent disclosure are discussed in terms of current limitingcomponents, it is fully contemplated that aspects of the presentdisclosure could be used in most any current inrush application withoutdeparting from the spirit of the invention.

A typical “inrush current limiter,” or ICL, limits inrush current byinitially impeding it with a desired amount of resistance, such as 10ohms of resistance, while at room temperature. When a high-currentdevice powers up, this initial resistance and in turn current drawcreates a lot of heat which causes the resistance of the ICL to dropover a 1-2 second period due to its negative temperature coefficient.Better said, as temperature increases the resistance decreases.

The “recovery time” for the ICL to cool back down to the original 10ohms is typically between 60-240 seconds. This time period is too longwhen being used with high current electric devices. Accordingly, thepresent disclosure is intended to speed up the cooling process.

The present disclosure details a soft starter to gradually ramp up thecurrent to an electrical device. The soft start function can be achieveda couple of ways. In a first aspect, a varying resistance (thermistor)can be placed in series between the high current electrical device andthe incoming electricity supply. The current will be lowered uponinitial powering up of the high current electrical device due to theresistance of the variable resistance thermistor. As the thermistorheats up the variable resistance drops to near zero due to heating fromthe introduction of electrical current and thus the high currentelectrical device is drawing all available current.

In a second aspect, power electronics are used to cool a resistance. Aprogrammable controller/triac (triode for alternating current) or SCR(silicon-controlled rectifier) circuit, over the course of a fewseconds, can adjust the amount of current that is supplied to the ACmotor.

Aspects of the present disclosure provide a temperature activated(thermistor) cooling fan. A plug-and-play, soft starter with a NEMA(National Electrical Manufacturers Association) standard plug andreceptacle is described below.

A current sensor and micro-controller are utilized in conjunction with abypass relay to aid in the “recovery” or cool down of soft startthermistors. Thus, aspects provide for a soft starter which can simplybe added-on to existing power tools and single-phase motors. Most softstarters existing today use VFD's or variable frequency drives. Theseare geared toward larger 3 phase motors and allow adjustment of softstart and soft stop functions. Some tool manufacturers build softstarters into their tools. The most effective way of performing this isby adding a “start winding” to the electric motor.

High inrush current produced when equipment is turned on may result indamage to electrical devices, adjacent devices and the personneloperating the electrical device. A safe and cost-effective way to reduceinrush current is to use an inrush current limiter, which is a specialtype of negative temperature coefficient (NTC) thermistor.

Typically, an NTC thermistor's resistance drops logarithmically as itstemperature increases when high current begins to flow through the NTCthermistor. An inrush current limiter is a component used to limitinrush current to avoid gradual damage to components and avoid blowingfuses or tripping circuit breakers. Negative temperature coefficient(NTC) thermistors and fixed resistors are often used to limit inrushcurrent. NTC thermistors can be used as inrush-current limiting devicesin power supply circuits when added in series with the circuit beingprotected. They present a higher resistance initially, which preventslarge currents from flowing at turn-on. As current continues to flow,NTC thermistors heat up, allowing higher current flow during normaloperation. NIT thermistors are usually much larger than measurement typethermistors and are purposely designed for power applications.

An NTC thermistor's resistance is low at high temperatures. When thecircuit is closed, the thermistor's resistance limits the initialcurrent. After some time, current flow heats the thermistor, and itsresistance changes to a lower value, allowing current to flowuninterrupted. It is inherently impossible for 100% of supply voltage toappear on the protected circuit, as the thermistor must continue todissipate power (i.e., producing heat) in order to maintain a lowresistance. The resulting voltage drop from the operating resistance,and the power consumption of the thermistor must be considered.

Inrush current limiting thermistors are usually disk-shaped, with aradial lead on each side. NTC resistor power handling is proportional toits size. NTC resistors are rated according to their resistance at roomtemperature.

Typically, an NTC thermistor's resistance drops logarithmically as itstemperature increases. The function of the NTC thermistor is to reducethe inrush current and then effectively remove itself from the circuit.The limiter blocks the incoming current spike by offering a relativelyhigh resistance upon power on. Typical resistance ranges are from 0.25ohm to 220 ohms, depending on the amount of protection desired. Ascurrent flows through to the NTC thermistor, the resistance drops to aslow as 0.01 ohm, which functionally removes it from the circuit.

Fixed resistors are also widely used to limit inrush current. These areinherently less efficient, since the resistance never falls from thevalue required to limit the inrush current. Consequently, they aregenerally chosen for lower power circuitry, where the additional ongoingpower waste is minor. Inrush limiting resistors are much cheaper thanthermistors. They are found in most compact fluorescent lamps (e.g.,light bulbs). They can be switched out of the circuit using a relay orMOSFET though, after inrush current is complete.

A typical application of inrush current limiters is in the input stageof non-power factor corrected switching supplies, to reduce the initialsurge of current from the line input to the reservoir capacitor. Themost popular application is the inrush protection of the AC current inswitching power supplies (SPS). The primary reason for having surgecurrent suppression in a SPS is to protect the diode bridge rectifier asthe input or charging capacitor is initially charged. This capacitordraws significant current during the first half AC cycle and can subjectthe components in line with the capacitor to excessive current. Theinitial equivalent series resistance (ESR) of the capacitor providesvery little protection for the diode bridge rectifier.

Typically, a thermistor is connected in series with a load. It isoperationally desirable to limit the time in which the resistance of thethermistor is high. Thus, it is highly desirable to quickly cooldown thethermistor after the load has reached steady-state conditions.

With reference to FIG. 1 an inrush current limiting circuit inaccordance with an aspect of the present disclosure is shown. Inrushcurrent limiting circuit 100 is shown having a housing enclosure 102,discussed in more detail in FIG. 2, an exhaust port 104, an electricalinput 106, an electrical output 108, one or more NTC or PTC thermistors110, an axial cooling fan 112, a temperature switch 114 and a printedcircuit board (PCB) 116.

In operation housing enclosure 102 can be made of most any material,such as a polymer. Housing enclosure 102 has PCB 116 mounted on aninterior wall. PCB 116 would have temperature switch 114, thermistors110 and cooling fan 112 all mounted on PCB 116. When electrical input106, a male electrical receptacle is plugged into a wall outlet,electrical power would stand readily available until an electricaldevice was plugged into the electrical outlet 108 and powered on, thuscompleting the circuit and allowing electricity to flow. During theinitial powering on of a high current electrical device, and discussedabove, a large amount of current would flow through the thermistors 110.This large amount of current would quickly heat up the thermistors andthus start lowering their resistive value.

Once temperature switch 114 reached a set temperature, a signal would besent to axial cooling fan 112 to power on and begin cooling thethermistors 110. This cooling of the thermistors would increase theresistance of the thermistors 110 and thus help in reducing the currentdelivered to the high current electrical device. The temperature couldbe preset in manufacturing and based upon the value of the thermistor110. For example, if the thermistors lose half their resistance at100-degree Fahrenheit, then the temperature switch 114 could be set to100 degrees Fahrenheit to begin cooling the thermistors 110 and thuscooling the thermistors 110 which in turn increases the resistance andincreases the current load, thus reducing current to the high currentelectrical device.

With reference to FIG. 2, a pictorial representation of a housingenclosure in accordance with an aspect of the present disclosure isshown. Housing enclosure 102 is shown with outlet 108 which can acceptthe male electrical connector of a high current electrical device. Input106 can be a male or female electrical connector. This would allowhousing enclosure 102 to be used most anywhere within a location withthe use of an extension between the wall outlet and the housingenclosure. However, it is preferable if the input 106 is a maleconnector to be plugged into most wall outlets or female connections ofan extension cord. At the bottom of enclosure 102 is an air vent inletfor cooling fan 112 to bring in outside cool air in which to cool offthe thermistors 110.

With reference to FIG. 3, a pictorial representation of an inrushcurrent limiting circuit in accordance with an aspect of the presentdisclosure is shown. Inrush current limiting circuit 300 has anenclosure 302, with exhaust vents 304, electrical input 306, and output308, PCB 310, a bypass relay 312, thermistors 314, axial cooling fan316, current sensor 318, microcontroller 320 and temperature sensor 322.

The inrush current limiting circuit 300 of FIG. 3, retains thethermistors 314, the axial cooling fan 316 and the temperature sensor322, but in this aspect current sensor 318 acts to sense activation orpowering on of the high current device coupled to outlet 308. Currentsensor 318 sends a signal to the micro-controller 320 to start a timer.Further, micro-controller 320 triggers bypass relay 312 when the timeris up and the current sensor 318 indicates the current flowing to thehigh current device is within a normal range and the inrush current hassubsided.

During the inrush current, the current flows through the thermistors314. As they are heated up, the temperature sensor 322 would start theaxial cooling fan 316 upon reaching a set temperature. Once currentsensor 318 determines a steady state of current exists, bypass relay 312bypasses the thermistors and routes the current directly to output 308.

With reference to FIG. 4, a pictorial representation of an inrushcurrent limiting circuit in accordance with an aspect of the presentdisclosure is shown. The aspect of FIG. 4 does not require an axialcooling fan. The aspect still has a current limiting circuit 400 and ahousing enclosure 401 having an electrical inlet 402 and outlet 404.Placed electrically in-between inlet 402 and outlet 404 is a currentsensor 410, such as a hall effect current sensor, a zero-crossingdetector 412, a microcontroller 406 and a Triac or SCR assembly 408.

In this aspect, current sensor 410 detects electric current in wire 414,and generates a signal proportional to the current. The generated signalcould be analog voltage or current or even a digital output.Zero-crossing detector 412 is a voltage comparator, used to detect asine waveform transition from positive and negative, coinciding when theincoming voltage crosses the zero-voltage condition.

The Triac SCR assembly 408 is used to reduce current in current-limitingcircuit 400. Micro-controller 406 controls the triac (triode foralternating current) SCR (silicon-controlled rectifier) circuit 408,over the course of a few seconds and can adjust the amount of currentsupplied to a high current electrical device.

In operation the microcontroller 406 receives a sensed current inputfrom current sensor 410. Further, zero-crossing detector 412 sends asignal to the microcontroller 406 notifying the microcontroller 406which phase, positive or negative the incoming alternating current iscurrently in. Based upon the current sensed at current sensor 410,microcontroller 406 controls the firing angle (portion of sine waveallowed to be passed through Triac 408) of the Triac 408, reducing it tozero degrees (full power) over a few seconds. For example, according toat least one aspect, using the reference from a zero-crossing circuit,the microcontroller 406 will pulse the gate of the Triac 408 when it isto allow the current to pass. The microcontroller 406 pulses accordingto the firing angle (or portion of sine wave conducted) that is writtenin software code loaded onto and operating on the microcontroller 406.In at least on aspect, the soft starter sine wave software code willfirst apply a higher firing angle (which limits output voltage andtherefore current), once a small predetermined current level is exceeded(sensed by the current sensor 410), the software program will gradually(over a 2 second period) reduce the firing angle to zero degrees,allowing full power from the Triac 408. In at least one configuration,software code operating microcontroller 406 can be programmed so ahigher firing angle=lesser portion of sine wave (lower voltage), lowerfiring angle=greater portion of sine wave (more voltage), and zerodegrees firing angle=full sine wave (full voltage/current).

A Triac (triode for alternating current) is a three terminal electroniccomponent conducting current in either direction when triggered. Alsoreferred to as a bidirectional triode thyristor or bilateral triodethyristor. A thyristor is analogous to a relay. A small voltage ofinduced current can control a much larger voltage and current. TRIACsare a subset of thyristors and are related to silicon-controlledrectifiers (SCRs). TRIACs differ from SCRs in they allow current flow inboth directions, whereas an SCR can only conduct current in a singledirection. Most TRIACs can be triggered by applying either a positive ornegative voltage to the gate (an SCR requires a positive voltage). Oncetriggered, SCRs and TRIACs continue to conduct, even if the gate currentceases, until the main current drops below a certain level called theholding current.

TRIACs' bidirectionality makes them convenient switches foralternating-current (AC). In addition, applying a trigger at acontrolled phase angle of the AC in the main circuit allows control ofthe average current flowing into a load (phase control).

With reference to FIG. 5, a pictorial representation of a housingenclosure in accordance with an aspect of the present disclosure isshown. Housing enclosure 401 is like housing enclosure 102 except thereis no need for an air vent 112 as there is no cooling fan required forcurrent limiting circuit 400. An electrical inlet 404 and an electricaloutlet 406 are shown on housing 401.

With reference to FIG. 6, a flowchart diagram of an inrushcurrent-limiting circuit operation in accordance with an aspect of thepresent disclosure is shown. Inrush current limiting program 600, canbegin at state 602 when a high current electrical device is eitherturned on or is sensed to be turned on by an inrush current circuit,such as 400, 300 or 100. At state 604, thermistors begin to heat fromcurrent flowing through. At state 606, temperature sensor 114 or 322senses the heat generated by thermistors 314 or 110 has exceeded apresent limit thus significantly reducing the resistance of thermistors314 or 110. At state 608, axial fan 316 or 112 is powered on to coolthermistors 110 or 314. At state 610, if the temperature of thermistors110 or 314 fall below the present limit, the axial fan 316 or 112 can bepowered off at state 612. Inrush current limiting program 600 thenreturns to state 606 to determine the temperature of the thermistors 114or 322. Or in some respects, the thermistors are bypassed once thecurrent has stabilized, such as in inrush current limiting circuit 300.

With reference to the figures using power control functions for limitingcurrent, what is disclosed generally is, a soft start subpanel 454 withhardwired current limiting circuit(s) 400 for providing dedicatedelectrical service to one or more hardwired outlets 404 within astructure 452 using a hardwired 450 electrical system and mainelectrical service panel 450 wired to a power source or electricalservice 448. The structure 452 can be any structure type with hardwired450 electrical service 448, such as a plant, manufacturing shop, andhome or mobile unit such as a motorhome, semi-trailer, and modular unit.In one aspect, electrical service 448, such as a 100-amp service line,can be run from a main electrical service panel 450 to a soft startsubpanel 454 within a hardwired electrical system of a structure 452.The soft start subpanel 454 can be configured with any number of softstart circuits 400, such as a one or more, two or more, three or more,four or more, and up to 8 or more soft start circuits 400 electricallyconnected and powered by electrical service 448, such as a 100-ampservice, from a main electrical service panel 450 within a structure452. Thus, a number of identical soft start circuits 400 on a circuitboard 405 of the subpanel 454 can be powered from a single electricalinput 448 from a main breaker box or main electrical service panel 450for providing power to a number of dedicated, soft start outlets 404hardwired 450 within a structure 452. The subpanel 454 can include acircuit board 405 configured with each of the soft start circuits 400.An exemplary circuit board 405 is shown in FIG. 7A-B, with FIG. 7Ashowing one side and FIG. 7B showing the opposite side. A dedicated,soft start electrical outlet 404 can be hardwired 450 to an outputterminal lug 428 of the subpanel 454. Each output terminal lug 428 ofthe subpanel 454 can be hardwired to a separate, dedicated soft startoutlet 404 within a structure 452. Thus, a structure 452 having a mainbreaker box/electrical service panel 450 with electrical service 440,such as a 100-amp service, can include one or more soft start subpanels454 for providing dedicated, hardwired 450 electrical service to one ormore dedicated, soft start outlets 404 within the structure 452.

The circuit board 405 providing current limiting circuits 400 can aninclude one or more input terminal lugs 418, such as for example,connecting to 120V or 240V service, and a corresponding neutral bar 424.The circuit board can include one or more transformers 416 for steppingthe voltage down to a lower voltage. In one aspect, the transformer 416can be 10:1 transformer for reducing 120V to 12V output for poweringelectronics on the circuit board 405 which are part of the currentlimiting circuit 400.

The circuit board 405 can be configured within a housing enclosure 401,such as a subpanel box. Current limiting circuits 400 can be housedwithin the subpanel box, such as on one or more printed circuit boards(PCBs) 405, having an electrical inlet 402 and one or more or aplurality of output terminal lugs 428 hardwired 450 to outlets 404.Placed electrically in-between inlet 402 and output terminal lugs 428one or more or a plurality of current sensors 410, such as a hall effectcurrent sensor, zero-crossing detectors 412 that can include, forexample, a diode bridge rectifier 456 and opto-coupler 458,microcontrollers 406 and Triacs or SCR assemblies 408, circuit breakers426, transformer(s) 416, capacitors 420, 422, 432, resistors 434, heatsinks 430, opto-isolators 436, and other PCT electronical components.

The current sensor 410 detects electric current in hardwire 450 andgenerates a signal proportional to the current. The generated signalcould be analog voltage or current or even a digital output.Zero-crossing detector 412 is a voltage comparator, used to detect asine waveform transition from positive and negative, coinciding when theincoming voltage crosses the zero-voltage condition.

The Triac 408 is used to reduce current in current-limiting circuit 400.Micro-controller 406 controls the Triac (triode for alternating current)SCR (silicon-controlled rectifier) circuit 408, over the course of a fewseconds, as best shown in FIG. 8, and can adjust the amount of currentsupplied to a high current electrical device plugged into hardwired 450outlets 404.

In operation microcontrollers 406 receives a sensed current input fromcurrent sensors 410. Further, zero-crossing detectors 412 send a signalto the microcontrollers 406 notifying the microcontrollers 406 whichphase, positive or negative the incoming alternating current iscurrently in. Based upon the current sensed at current sensors 410,microcontrollers 406 control the firing angle (portion of sine waveallowed to be passed through Triacs 408) of the Triacs 408, reducing itto zero degrees (full power) over a few seconds. For example, accordingto at least one aspect, using the reference from a zero-crossingcircuit, the microcontroller 406 will pulse the gate of the Triac 408when it is to allow the current to pass. The microcontroller 406 pulsesaccording to the firing angle (or portion of sine wave conducted) thatis written in software code loaded onto and operating on themicrocontroller 406. In at least on aspect, the soft starter sine wavesoftware code will first apply a higher firing angle (which limitsoutput voltage and therefore current) as shown in Step 438 of FIG. 8. Ifthe current detected does not exceed a preset or predetermined currentlevel as shown in Step 442 of FIG. 8 the software loaded onmicrocontrollers 406 maintains a higher firing angle for Triacs 408 socircuit is set to reduced voltage and current potential (Step 438). Oncea small predetermined current level is exceeded (sensed by the currentsensor 410) as shown in Step 440 of FIG. 8, the software program willgradually (over a 2 second period) reduce the firing angle to zerodegrees (Step 446), allowing full power from the Triac 408. In at leastone configuration, software code operating microcontrollers 406 can beprogrammed so a higher firing angle=lesser portion of sine wave (lowervoltage), lower firing angle=greater portion of sine wave (morevoltage), and zero degrees firing angle=full sine wave (fullvoltage/current). When the current returns to a level that does notexceed a preset or predetermined current level (Step 442), such as whena universal or induction motor connected to an outlet 404 is turned off,the software code operating microcontrollers 406 set the Triac to arelatively high degree firing angle so circuit is set to reduced voltageand current potential (Step 438).

During operation, transformer(s) 416 reduces the voltage for poweringthe software code operating microcontrollers 406 with, for example, 12Vinstead of 120V. The circuit can include one or more heat sinks 430 fordissipating heat from the Triacs 408 and other circuitry components. Thecircuit includes one or more circuit breakers 426, such as 25 A circuitbreaker for a 20 A circuit, to maintain, for example, a safety rating of115% of the amperage rating for a motor connected to an outlet 404.Other amperage circuit breakers can be used based on the need at outlet404. Opto-isolator(s) 436 isolate, for example, using light, theTriac(s) 408 input from other circuitry components of each currentlimiting circuit 400.

Each outlet 404 has a dedicated current limiting circuit 400 withinsubpanel 454. This allows the subpanel 454 and circuit board 405 to beconfigured for a multitude of uses. In one aspect, current can belimited in one outlet 404 and not limited in another outlet 404 usingthe current limiting circuits and software controlled microcontrollers406. For example, a saw motor can be connected to hardwired outlet 404and a dust vacuum can be connected to another hardwired 450 outlet 404.The power limiting circuit can increase voltage and current over time tothe saw motor and at the same time power on the dust vacuum. In anotherconfiguration, software code for the microcontroller 406 for the circuit440 connected to the duct vacuum can be rewritten to soft start outlet404 connected to the dust vacuum. Thus, the subpanel 454 can beconfigured with a number of soft start circuits 400 each hardwired 450to a dedicated outlet 404 for controlling voltage and current over time,if desired, to any electrically powered device plugged into hardwired450 outlet(s) 404.

The subpanel 454 can be configured to for handling split phase (240V)service. Two Triacs 408 are configured for controlling each phase of120V. One Triac 408, for example, could control power and current to asaw motor and the other Triac 408, for example, could control power andcurrent to a dust vacuum. The current limiting circuit(s) 400 can beconfigured within a subpanel 454 as shown in the figures or in aplug-n-play (module) housing enclosure 401 with pigtails connections106, 108 for connecting to input and output terminal lugs of theenclosure, such as shown in FIG. 5. The housing enclosure 401 cansubpanel box 454. The housing enclosure 401 can be a portable unit thatis not hardwired. Configurations can range from single phaseconfiguration having one, two or more outlets 404. Commercial units canbe range from a single phase configuration having four, eight or moreoutlets 404. Units can be configured for split phase power, such as240V, split phase power having two 120V hot legs with two separate busbars for feeding half the output terminal lugs 428 with one hot leg andthe other output terminal lugs 428 with the other hot leg. The unitcould be configured with a power limiting circuit for 240V soft startoutlet 404 at 20A or a 240V soft start outlet 404 at 30A depending onneed. On one aspect, a unit could be configured to split the twoincoming phases of power and run each phase through separate 120V powerlimiting circuits 400 at, for example, 15 A, per circuit. A unit can beconfigured to separate and control two phases of power independently,such as where power is provided to operate a saw motor and vacuum motorindependently and using on one or both phases of power the powerlimiting functionality of the present disclosure. The concepts of thepresent disclosure provide for the combination of 120V and 240V powerusing soft start circuits 400, where instead of a having a 120V inputand a neutral, configurations also include having two 120V hot leginputs that are out of phase along with a neutral input. One phase couldbe wired to, for example, four soft start circuits 400 and the otherphase wired to four additional soft start circuits 400. By way offurther example, 120V power could be connected to any one of outputterminal lugs 428 or to an electrical outlet 404, whether a pigtail orhardwired; similarly, 240V could be used by connected each of the 120Vhot legs to each of the 120V output terminal lugs 428, outlets 404 orpigtail outlet (power cord) 404. In another example, eight outputterminal lugs 428 or outlets 404 can be provided by configuring fouroutputs/outlets as 240V soft start outputs/outlets, eightsoutputs/outlets as 120V soft start outputs/outlets, or four 120V softstart outputs/outlets and two 240V soft start outlets. In anotherexample, the one or more soft start outputs/outlets can be a regular,non-soft start output/outlet in combination with one or more soft startoutput(s)/outlet(s), based on need or preference.

The configurations of the present disclosure offer significant safetyfeatures and functionality to keep users safe from shock andelectrocution, while also protecting electrical power consuming devicesfrom being harmed. For example, the circuits 400 are set to reducedvoltage and current potential and any immediate current draw is verylimited, thus resulting in very little chance for shock more than atingle and/or electrocution. In another example, if during reduction ofthe firing angle of the Triac 408 thus resulting in increased voltageand current over time, if an outlet/output wire of the circuit wereaccidentally cut it would trip circuit breaker(s) 426.

The power limiting circuit(s) 400 of the present disclosure can beimplemented within a housing enclosure 401 of varying shape, size,proportion, input voltage, output voltage, amperage, etc., as best shownin FIGS. 9A-C. Written description is not limited to the drawing(s) forwhich it describes. For example, the description for aspects of thecurrent limiting circuit 400 described relative to use in a subpanel 454within a hardwired structure as shown in FIGS. 7A-C can be implementedinto a housing enclosure 401 that is portable as shown in the otherFigures, such as FIGS. 4, 5 and 9.

The disclosure is not to be limited to the aspects described herein. Inparticular, the disclosure contemplates numerous variations in inrushcurrent limiting. The foregoing description has been presented forpurposes of illustration and description. It is not intended to be anexhaustive list or limit any of the disclosure to the precise formsdisclosed. It is contemplated that other alternatives or exemplaryaspects are considered included in the invention. The description ismerely examples of aspects, processes or methods of the invention. It isunderstood that any other modifications, substitutions, and/or additionscan be made, which are within the intended spirit and scope of theinvention.

What is claimed is:
 1. An inrush current limiting circuit, comprising:an electrical input and an electrical output connected to a printedcircuit board; a current limiting circuit connected between theelectrical input and the electrical output, the current limiting circuitfor increasing voltage and current over time from the electrical inputto the electrical output by operation of a current sensor and amicrocontroller; an electrical enclosure having the electrical input andthe electrical output, wherein the electrical input is configured toconnect to an electrical service and the electrical output is configuredto provide connection to the electrical service by the current limitingcircuit.
 2. The circuit of claim 1, wherein the electrical inputcomprises an electrical service input connector.
 3. The circuit of claim1, wherein the electrical output comprises an electrical service outputconnector.
 4. The circuit of claim 1, wherein the current limitingcircuit comprises a triode for alternating current.
 5. The circuit ofclaim 1, wherein the current sensor comprises a hall effect currentsensor.
 6. The circuit of claim 1, wherein the current limiting circuitcomprises a zero-crossing detector for sending a signal to themicrocontroller for the phase of incoming alternating current from theelectrical service.
 7. The circuit of claim 1, wherein the electricalinput comprises a pigtail connected electrical connector.
 8. The circuitof claim 1, wherein the electrical output comprises a pigtail connectedelectrical connector.
 9. A portable inrush current limiting circuit andhousing, comprising: a portable electrical current limiting circuitcomponent housing; an electrical input connected to the housing, theelectrical input configured for connection to an electrical service; anelectrical output connected to the housing, the electrical outputconfigured for connection to an electrical consuming device or circuit;a current limiting circuit connected between the electrical input andthe electrical output, the current limiting circuit for increasingvoltage and current over time from the electrical input to theelectrical output by operation of a current sensor and amicrocontroller.
 10. The circuit and housing of claim 9, wherein theelectrical input comprises an electrical input connector disposed on thehousing.
 11. The circuit and housing of claim 9 wherein the electricalinput comprises an electrical input connector hardwired to and extendingfrom the housing.
 12. The circuit and housing of claim 9, wherein theelectrical output comprises an electrical output connector disposed onthe housing.
 13. The circuit and housing of claim 9, wherein the currentlimiting circuit comprises a triode for alternating current.
 14. Thecircuit and housing of claim 9, wherein the current sensor comprises ahall effect current sensor.
 15. The circuit and housing of claim 9,wherein the current limiting circuit comprises a zero-crossing detectorfor sending a signal to the microcontroller for the phase of incomingalternating current from the electrical service.
 16. A method forincreasing voltage and current over time from an electrical input to anelectrical output by operation of a current limiting circuit, the methodcomprising: providing a portable electrical current limiting circuitcomponent housing, an electrical input configured for connection to anelectrical service and an electrical output configured for connection toan electrical consuming device or circuit, and a current limitingcircuit connected between the electrical input and the electricaloutput; increasing voltage and current over time from the electricalinput to the electrical output by operation of a current sensor and amicrocontroller of the current limiting circuit.
 17. The method of claim16, further comprising: detecting current draw with the current sensor.18. The method of claim 16, further comprising: determining a phase ofincoming alternating current from the electrical service with azero-crossing detector.
 19. The method of claim 16, further comprising:operating the microcontroller with software code loaded onto themicrocontroller for controlling current differently to two or more ofthe electrical outputs.
 20. The method of claim 16, further comprising:receiving a startup command at the current limiting circuit from theelectrical consuming device or circuit connected to the housing via theelectrical input.